About this replacement
Lenovo IdeaPad Flex 5 14IAU7 — 11.52V Li-Polymer Replacement Battery (5B11F38035)
This is an 11.52V, 4400mAh (50.69Wh) lithium-polymer battery for the Lenovo IdeaPad Flex 5 14-inch 2-in-1 convertible laptop. It covers the 14IAU7 and 14ALC7 series, including model 82R7006TUK and over 126 additional variants. The OEM part numbers 5B11F38035, 5B11F38038, L21B3PE0, L21C3PE0, L21D3PE0, and related codes all cross to this cell.
- Flex 5 14IAU7 and 14ALC7 compatibility: Both the Intel IAU7 and AMD ALC7 Flex 5 platforms share the same 11.52V three-cell architecture and identical connector pinout, so one battery covers both processor variants without modification.
- Bench tested on actual hardware: We ran this cell through charge, discharge, and BMS handshake cycles on the Flex 5 platform. The BMS negotiated charge correctly, the fuel gauge IC responded, and no fault codes were logged during the test sequence.
- Post-install calibration on the Flex 5: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on these models.
BIOS reporting poor battery health immediately after replacement
The Flex 5 BIOS reads cycle count and health data stored in the old cell's EEPROM. When a new cell goes in, that EEPROM data is blank or mismatched, and the BIOS flags it as degraded. This is not a fault with the replacement cell — it is a firmware artefact. Running the battery learn cycle (full discharge to hibernate, then uninterrupted charge to 100%) gives the BIOS enough data to recalculate health correctly. After one or two full cycles, the health status clears.
Laptop shuts down at 20–30% remaining after battery swap
This happens because the fuel gauge IC is still calibrated to the discharge curve of the old, degraded cell. The new cell has a different voltage-versus-capacity curve, so the gauge hits its cutoff threshold well before the cell is actually empty. The fix is to complete two to three full discharge-to-hibernate and full-charge cycles without interruption. Once the IC has mapped the new cell's curve, the reported percentage will align with actual remaining capacity, and the premature shutdowns stop.